A carbon-coated active material glass powder, a preparation method thereof, and applications thereof

Abstract

The present invention provides a carbon-coated active material glass powder, a preparation method thereof and an application thereof; the raw materials for preparing the carbon-coated active material glass powder include: a glass network former, a transition metal oxide V2O5 and an impregnating solution; the impregnating solution includes asphaltene and ammonium fluoride. In the present invention, a glass block is prepared by melting and quenching the glass network former and the transition metal oxide V2O5, ground and then fully mixed with the impregnating solution, and after filtration, carbonization treatment is carried out to obtain the carbon-coated active material glass powder. This powder is applied in a lithium-ion battery, and the conductivity is 9×10 ‑4 ~4×10 ‑4 S / m; the charge transfer impedance is 423~201Ω; the coefficient of thermal expansion is 7×10 ‑6 ~4×10 ‑6 / K; the initial discharge specific capacity is 275~286mAh / g; the discharge capacity of the battery after 100 cycles is 257~274mAh / g, and the cycle efficiency is 93%~96%.

Description

Technical Field

[0001] The present invention belongs to the technical field of cathode materials, and particularly relates to a carbon-coated active substance glass powder, a preparation method thereof, and an application thereof. Background Art

[0002] High-performance energy storage devices are a major demand in China. Lithium ions have the advantages of high energy density, environmental friendliness, ultra-long cycle life, superior energy conversion efficiency, high-rate charge-discharge process, and no obvious memory effect.

[0003] Currently, commercial lithium-ion cathode materials are mainly composite lithium-containing oxides (ternary) such as cobalt, manganese, nickel, and lithium iron phosphate, etc. However, they are still limited by low energy density, and the specific capacity is significantly lower than the market's expected requirements. The multi-electron reaction of transition metal (TM) elements is regarded as one of the effective methods to improve the capacity. The multi-electron reaction means that multiple Li + ions can be intercalated and deintercalated, thereby achieving a higher specific capacity and then enhancing the energy density. Among many transition metal elements, vanadium has multiple stable oxidation states, and the common valence states are +5, +4, +3, +2, etc. Vanadium-based materials represented by V2O5 are a typical type of materials that can achieve multi-electron reactions due to the variable valence state of vanadium.

[0004] Whittingham proposed that today's commercialization can only reach 25% of its theoretical capacity. In the lithium field, one way to increase the energy density and simultaneously reduce the cost is to perform multiple single-electron reactions at each redox center. For example, it can be achieved by intercalating two lithium / sodium ions or one magnesium / calcium into the host structure. Within the stability limit of today's electrolytes, few transition metals have two redox pairs. Fortunately, V is one of them, and its redox reaction can easily occur between the +5 and +2 states. Vanadium has rich reserves and is the fourth transition metal element, more than nickel and cobalt currently in use. During the multiple Li + intercalation-deintercalation process, the serious structural deterioration and rapid capacity decay of vanadium-based crystalline nanomaterials are common problems faced by these materials.

[0005] V2O5 is an amphoteric acid-base oxide, which has limitations such as fast dissolution rate, irreversible phase change, severe volume expansion, and low electronic conductivity. Therefore, many strategies have been explored to improve the performance of vanadium-based electrode materials, such as studying strategies of bulk structure transformation, mixing of conductive substances, element doping, valence bond transformation, disordered rock salt, and crystalline state transformation. The crystalline V2O5 melt quenching process can be changed into an amorphous state, and no phase change occurs in the lithiated product amorphous Li x V2O5. Glass, as a typical amorphous material, has begun to be studied as an electrode material due to its special structural characteristics. Amorphous vanadium-based glass materials have an open network structure, no grain boundaries, and can intercalate and deintercalate Li+ and other characteristics, it is considered a suitable electrode material for lithium batteries. V2O5-based glasses are suitable electrode materials for lithium batteries, such as vanadium-phosphorus glass electrodes (P2O5-V2O5, etc.), vanadium-boron glass electrodes (V2O5-LiBO2, etc.), vanadium-tellurium glass electrodes (TeO2-V2O5, etc.), vanadium-silicon glass electrodes (SiO2-V2O5, etc.).

[0006] The V2O5-P2O5 glass synthesized in a reducing atmosphere (H2) has higher capacity, excellent rate performance, and stable cycling performance compared to the glass synthesized in air atmosphere. A larger number of V 4+ / V 3+ redox pairs improve the conductivity and reduce the irreversible capacity loss in the first cycle. Similarly, carbon-coated Li2O-V2O5-P2O5 glass-ceramics precipitate the crystalline phases V2O3 and VO2, which have good conductivity and structural ductility as the cathode material for lithium-ion batteries. Conductivity is one of the important performance indicators of vanadium-based glass lithium battery electrode materials.

[0007] It is considered an effective way to improve the rate performance and cycling performance of V2O5 materials by surface coating with conductive coatings, doping with conductive substances, reducing particle size, etc. Coating with carbonaceous substances, such as carbon nanotubes, graphene, etc., has good electronic conductivity and shortens the lithium-ion diffusion length, thus ensuring high rate performance. Mixing V2O5 with conductive substances (polyaniline (PANI), polypyrrole (PPY), poly(3,4-ethylenedioxythiophene) (PEDOT), Cu, conductive metal fabric) can improve its performance. Adding conductive additives can prevent aggregation and improve the effective conductivity of the entire electrode material. However, the poor electrical contact at the interface between V2O5 nanoparticles and carbon additives and the lack of a continuous carbon skeleton still limit the achievement of high specific capacity of these materials at higher power rates. Petroleum asphalt is the residue after crude oil distillation, and its main uses are as infrastructure materials, raw materials, and fuels. Currently, it has the characteristics of overcapacity, low price, difficult processing, environmental pollution, and serious waste. Currently, the application process of converting asphalt to prepare carbon material anodes is challenging. SUMMARY OF THE INVENTION

[0008] In view of this, the purpose of the present invention is to provide a carbon-coated active substance glass powder, its preparation method, and its application. As the active component of the cathode material, the assembled battery has advantages such as large specific capacity, high voltage, and small first-cycle loss rate.

[0009] The present invention provides a carbon-coated active substance glass powder, and the preparation raw materials include a glass network former, a transition metal oxide V2O5, and an impregnating solution;

[0010] The impregnating solution includes asphaltene and ammonium fluoride.

[0011] In the present invention, the mass ratio of the glass network former, the transition metal oxide, and the impregnating solution is (10 - 30):(30 - 70):(20 - 40);

[0012] The mass ratio of the solvent, asphaltene, and ammonium fluoride in the impregnating solution is (15 - 68):(30 - 83):(2 - 10).

[0013] In the present invention, the glass network former is selected from one or more of TeO2, Li3PO4, P2O5, SiO2, and LiBO2.

[0014] In the present invention, the solvent is selected from one or more of toluene, benzene, xylene, and tetrahydrofuran.

[0015] In the present invention, the particle size of the asphaltene is 200 - 500 μm.

[0016] The present invention provides a method for preparing the carbon-coated active substance glass powder according to the above technical solution, comprising the following steps:

[0017] Mix the glass network former and the transition metal oxide V2O5, and use the melt quenching method under an inert atmosphere, grind and screen to obtain vanadium-based glass powder;

[0018] Mix the vanadium-based glass powder and the impregnating solution, filter, and carbonize to obtain the carbon-coated active substance glass powder.

[0019] In the present invention, the carbonization specifically includes:

[0020] Under an N2 atmosphere, heat up to 1500 - 1800 °C, keep warm for 10 - 300 min; then continue to heat up to 2000 - 3000 °C, keep warm for 10 - 30 min, and cool to obtain the carbon-coated active substance glass powder.

[0021] In the present invention, the melt quenching method under an inert atmosphere specifically includes:

[0022] Heat the mixture to 500 - 800 °C under an inert atmosphere, keep warm for 10 - 300 min, then continue to heat up to 1000 - 2000 °C, keep warm for 10 - 30 min, and cool to obtain a glass block.

[0023] The present invention provides an amorphous cathode material, comprising the carbon-coated active substance glass powder, a binder, and a conductive filler according to the above technical solution;

[0024] The mass ratio of the carbon-coated active substance glass powder, the binder, and the conductive filler is (6 - 10):(2 - 3):(1 - 2).

[0025] The present invention provides a lithium-ion battery, which includes the amorphous cathode material described in the above technical solution.

[0026] The present invention provides a carbon-coated active substance glass powder, and the preparation raw materials include: a glass network former, a transition metal oxide V2O5, and an impregnating solution; the impregnating solution includes asphaltene and ammonium fluoride. The present invention prepares a glass block by melting and quenching the glass network former and the transition metal oxide V2O5, grinding it and fully mixing it with the impregnating solution, and performing carbonization treatment after filtration to obtain the carbon-coated active substance glass powder. When this powder is applied in a lithium-ion battery, the conductivity is 9×10 -4 ~4×10 -4 S / m; the charge transfer impedance is 423~201Ω; the thermal expansion coefficient is 7×10 -6 ~4×10 -6 / K; the initial discharge specific capacity is 275~286mAh / g; the discharge capacity of the battery after 100 cycles is 257~274mAh / g, and the cycle efficiency is 93%~96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the X-ray diffraction (XRD) pattern of the vanadium-based glass powder and the carbon-coated active substance glass powder prepared in Example 4 of the present invention;

[0028] Figure 2 It is the scanning electron microscope (SEM) image of the carbon-coated active substance glass powder prepared in Example 4 of the present invention;

[0029] Figure 3 It is the charge-discharge cycle curve of the lithium-ion battery assembled in Example 4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention provides a carbon-coated active substance glass powder, and the preparation raw materials include a glass network former, a transition metal oxide V2O5, and an impregnating solution;

[0031] The impregnating solution includes asphaltene and ammonium fluoride.

[0032] By using ammonium fluoride in the present invention, it decomposes into NH3 and HF during carbonization, and HF migrates and supplements the vacancies caused by the S element of asphaltene under the influence of hydrogen bonds, improving the conductivity of the vanadium-based glass, reducing the charge transfer impedance, and improving the problems of excessive loss of the first-cycle specific capacity and low capacity retention rate after cycling.

[0033] The preparation raw materials of the carbon-coated active substance glass powder provided by the present invention include a glass network former; the glass network former is selected from one or more of TeO2, Li3PO4, P2O5, SiO2, and LiBO2.

[0034] The raw materials for preparing the carbon-coated active material glass powder include the transition metal oxide V2O5. The glass network former and V2O5 are used to prepare a vanadium-based glass block by the melt quenching method.

[0035] The raw materials for preparing the carbon-coated active material glass powder include an impregnating solution; the impregnating solution includes asphaltene and ammonium fluoride. The impregnating solution further includes a solvent, and the solvent is selected from one or more of toluene, benzene, xylene, and tetrahydrofuran; the solvent such as toluene is thermally transformed into C and water vapor.

[0036] In the present invention, the mass ratio of the solvent, asphaltene, and ammonium fluoride in the impregnating solution is (15 - 68):(30 - 83):(2 - 10). In a specific embodiment, the mass ratio of the solvent, asphaltene, and ammonium fluoride in the impregnating solution is 20:75:5.

[0037] In the present invention, the asphaltene is prepared by the following method:

[0038] Using pentane as a solvent, it is mixed with heavy oil for extraction under near-critical conditions, deasphalted oil and raffinate asphalt are obtained in an extraction tower, and the raffinate asphalt is granulated to obtain asphaltene with an average particle size of 200 - 500 μm.

[0039] In the present invention, the raffinate asphalt is directly introduced into a granulation tower for granulation; granulation is carried out and gas-solid separation from the solvent is achieved.

[0040] The deasphalted oil is further heated and raised in temperature, the gum phase and the light deasphalted oil phase are separated, the light deasphalted oil enters a supercritical solvent recovery tower, and 85% of the solvent is directly recovered and recycled under high pressure under supercritical conditions.

[0041] In the present invention, the asphaltene is dissolved with a solvent, and an ammonium fluoride additive is added to prepare an impregnating solution. In the present invention, the mass ratio of the glass network former, transition metal oxide, and impregnating solution is (10 - 30):(30 - 70):(20 - 40); in a specific embodiment, the mass ratio of the glass network former, transition metal oxide, and impregnating solution is 10:50:40; or 15:60:25; or 20:50:30; or 25:55:20; or 10:70:20.

[0042] In the present invention, the ammonium fluoride increases the solubility of asphaltene powder in toluene. During the carbonization treatment process, the core of the asphaltene molecule is transformed into few-layer carbon materials by eliminating alkyl side chains, peeling aromatic layers, and expanding the aromatic layer diameter; toluene is thermally transformed into C and water vapor; the S element is thermally transformed into a gas and precipitated with N2; ammonium fluoride decomposes into NH3 and HF, and HF migrates and supplements the vacancies caused by the S element under the influence of hydrogen bonds, and NH3 is precipitated with N2. Asphaltene forms an amorphous carbon layer on the surface of the vanadium-based glass powder material to construct a "core-shell structure".

[0043] The present invention provides a method for preparing the carbon-coated active material glass powder described in the above technical solution, comprising the following steps:

[0044] A mixture of a glass network former and a transition metal oxide V2O5 is melt-quenched in an inert atmosphere, and then ground and sieved to obtain a vanadium-based glass powder;

[0045] The vanadium-based glass powder and the impregnation solution are mixed, filtered, and carbonized to obtain carbon-coated active material glass powder.

[0046] The invention adopts a melting quenching method to prepare a mixture of a glass network former and a transition metal oxide V2O5 in an inert atmosphere, and grinds and sieves the mixture to obtain vanadium-based glass powder.

[0047] In the present invention, the melt quenching method under an inert atmosphere specifically includes:

[0048] The mixture is heated to 500-800° C. in an inert atmosphere, kept warm for 10-300 minutes, then continued to be heated to 1000-2000° C., kept warm for 10-30 minutes, and cooled to obtain a glass block.

[0049] The inert atmosphere is N2 or argon.

[0050] The present invention fully grinds the glass block, and sieves it to select vanadium-based glass powder with a particle size less than 5 microns.

[0051] The present invention mixes the vanadium-based glass powder and the impregnation liquid, filters, and carbonizes to obtain carbon-coated active material glass powder. The present invention preferably transfers the vanadium-based glass powder into the impregnation liquid, stirs and mixes it thoroughly, filters out the liquid, pours it into a stirring and heating kettle, and carbonizes it, and passes N2 gas into the kettle.

[0052] In the present invention, the carbonization specifically includes:

[0053] In a N2 atmosphere, the temperature is raised to 1500-1800°C and kept at this temperature for 10-300 minutes; the temperature is then further raised to 2000-3000°C and kept at this temperature for 10-30 minutes, and the mixture is cooled to obtain a carbon-coated active material glass powder.

[0054] In the present invention, the gas in the kettle is preferably connected to a caustic soda solution for tail gas absorption treatment.

[0055] The present invention places the carbon-coated active material glass powder in a dry environment for subsequent testing and use.

[0056] The present invention also provides an amorphous cathode material, comprising the carbon-coated active substance glass powder, binder and conductive filler as described in the above technical solution; the mass ratio of the carbon-coated active substance glass powder, binder and conductive filler is (6-10):(2-3):(1-2). The binder is selected from polyvinylidene fluoride; the conductive filler is selected from conductive carbon black.

[0057] The present invention also provides a lithium-ion battery, comprising the amorphous cathode material as described in the above technical solution.

[0058] Due to the adoption of the carbon-coated active substance glass powder in the positive electrode, the above lithium-ion battery has high conductivity, large specific capacity and small loss rate.

[0059] In order to further illustrate the present invention, a carbon-coated active substance glass powder, its preparation method and its application provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0060] Example 1

[0061] By weight, 10 parts of TeO2 and 50 parts of V2O5 are proportioned and mixed, stirred and ground evenly, and the obtained mixed raw materials are transferred to an alumina crucible. It is melted in a tube furnace under argon protection, heated at a heating rate of 5 °C / min to 700 °C, and kept warm for 100 min; then the temperature is raised to 1000 °C at a heating rate of 15 °C / min and kept warm for 30 min; the mixed liquid is quickly poured onto the surface of liquid tin to form glass. The glass liquid spreads out and flattens on the tin liquid surface, forming a flat upper and lower surface, hardening, and cooling and then being led onto a transition roller table. The rollers of the roller table rotate, pulling the glass belt out of the tin bath and into an annealing furnace, the furnace body temperature is 200 °C, and after annealing for 300 min, a glass block is obtained. It is fully ground using a ball mill, and the vanadium-based glass powder with a particle size less than 5 microns is selected by sieving;

[0062] The solvent is selected from one or more of benzene, xylene and tetrahydrofuran; the solvent such as toluene is thermally transformed into C and water vapor.

[0063] 20 parts of the solvent toluene are used in a stirring kettle, 75 parts of asphaltene and 5 parts of ammonium fluoride additive are respectively added, and they are fully mixed and stirred to dissolve, obtaining an impregnating solution.

[0064] The above vanadium-based glass powder is poured into 40 parts of the impregnating solution, fully mixed, filtered, and carbonized. The atmosphere in the kettle is filled with N2 gas, heated to 1500-1800 °C, kept warm for 10-300 min, then continuously heated to 2000-3000 °C, kept warm for 10-30 min, and cooled to form, obtaining the carbon-coated active substance glass powder. The gas in the kettle is connected to a caustic soda solution for tail gas absorption treatment;

[0065] The cathode active material glass powder, binder (polyvinylidene fluoride), and conductive carbon black (particle size distribution 1 - 10 μm) powder with a mass ratio of 7:2:1 were mixed, and then an appropriate amount of solvent N-methylpyrrolidone (20 wt% of the powder) was dropped in and ball-milled. The resulting slurry was coated on aluminum foil and dried. After vacuum drying at 60 °C for 12 hours, it was cut into discs with a diameter of 12 mm and used as the positive electrode. A lithium sheet was used as the reference electrode, and 1 M LiPF6 in a mixture of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (1:1:1 v / v / v) was used as the electrolyte. A CR2032 coin cell was prepared in a glove box filled with argon (H2O < 0.1 ppm, O2 < 0.1 ppm). The cycling performance of the battery was tested using a LAND CT3001A battery test system. And an electrochemical impedance spectroscopy (EIS) test was performed using a CHI660E, and the recorded frequency range was 10 -2 ~10 5 Hz, with an amplitude of 5 mV.

[0066] Examples 2 - 5

[0067] According to the process flow of Example 1, different glass network formers TeO2 or Li3PO4 or P2O5 or SiO2 or LiBO2, transition metal oxide V2O5, and the mass of the impregnating solution are shown in Table 1:

[0068] Table 1 Types and dosages of raw materials used in Examples 1 - 5

[0069]

[0070] Comparative Example 1

[0071] The dried V2O5 powder and P2O5 powder were mixed in a stoichiometric ratio and melted in a hydrogen atmosphere to obtain an 80V2O5·20P2O5 glass sample. The mixture was placed in a quartz crucible after stirring and uniform mixing. Glass melting was carried out using a tube furnace. It was heated at 800 °C for 5 min to obtain a melt of the vanadium phosphorus glass sample. The molten glass was poured onto an iron plate and then annealed in a muffle furnace at 250 °C for 2 h, and then cooled in the furnace. The pre-prepared glass was ground into powder with a particle size < 20 μm using an agate mortar.

[0072] The electrode is made of active material (vanadium phosphorus glass powder), carbon black and polytetrafluoroethylene (PTFE) binder mixed in a mass ratio of 8:1.5:0.5. The weighed vanadium phosphorus glass powder and carbon black are put into an agate mortar and ground for 30 minutes to obtain a uniform mixture. Then, polytetrafluoroethylene is added to the prepared mixture and vigorously mixed to obtain a uniform film (thickness 80μm). The prepared cathode film is punched into discs with a circular cutter with a diameter of 8mm and evenly pasted on an aluminum mesh. Then, a CR2032 coin cell (316L stainless steel, polypropylene gasket) is used as the cathode, 1mol / LLiPF6 is used as the ethylene carbonate / dimethyl carbonate (volume ratio 1:1) electrolyte, Celgard 2025 is used as the diaphragm, and the lithium sheet is used as the counter electrode. The charge and discharge performance of the comparative lithium-ion battery at different current densities in the voltage range of 2.0 to 4.2V is tested on an electrochemical workstation. Test data shows that for the first time with 270mAh g -1 The specific capacity of the battery is 2.57W, with a capacity retention rate of about 90% after 100 cycles. In addition, after 300 cycles, the battery has a capacity retention rate of about 90% after 100 cycles. -1 The high current density can provide 220mAh g -1 The specific capacity is equivalent to 80% capacity retention rate.

[0073] Comparative Example 2

[0074] Based on Example 1, the difference is that the raw materials are mixed with 10 parts of TeO2 and 50 parts of V2O5, and the impregnation treatment with impregnation liquid is not used. The other process parameters are the same as those in Example 1.

[0075] The present invention tests the performance of lithium-ion batteries assembled with glass positive electrode materials prepared in the examples and comparative examples, and the results are shown in Table 2:

[0076] Table 2 Performance test results of batteries prepared in Examples and Comparative Examples

[0077]

[0078] As can be seen from the above embodiments, the present invention provides a carbon-coated active material glass powder, the raw materials for preparation include: glass network former, transition metal oxide V2O5 and impregnation solution; the impregnation solution includes asphaltene and ammonium fluoride. The present invention prepares a glass block by melting and quenching the glass network former and transition metal oxide V2O5, grinds it and mixes it with the impregnation solution, and then carbonizes it after filtering to obtain a carbon-coated active material glass powder. The powder is used in lithium-ion batteries, and the conductivity is 9×10 -4 ~4×10 -4 S / m; charge transfer impedance 423~201Ω; thermal expansion coefficient 7×10-6 ~4×10 -6 / K; The initial discharge specific capacity is 275 - 286 mAh / g; The discharge capacity of the battery after 100 cycles is 257 - 274 mAh / g, and the cycle efficiency is 93% - 96%.

[0079] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A carbon-coated active substance glass powder, the preparation raw materials including: A glass network former, a transition metal oxide V2O5, and an impregnating solution; The impregnating solution includes asphaltene, a solvent, and ammonium fluoride; The glass network former is selected from one or more of TeO2, Li3PO4, P2O5, SiO2, and LiBO2.

2. The carbon-coated active material glass powder according to claim 1, characterized in that, The mass ratio of the glass network former, the transition metal oxide, and the impregnating solution is (10~30) : (30~70) : (20~40); The mass ratio of the solvent, asphaltene, and ammonium fluoride in the impregnating solution is (15~68) : (30~83) : (2~10).

3. The carbon-coated active material glass powder according to claim 2, wherein The solvent is selected from one or more of toluene, benzene, xylene, and tetrahydrofuran.

4. The carbon-coated active material glass powder according to claim 1, characterized in that, The particle size of the asphaltene is 200~500μm.

5. A preparation method of the carbon-coated active substance glass powder according to any one of claims 1~4, comprising the following steps: Melting and quenching a mixture of the glass network former and the transition metal oxide V2O5 in an inert atmosphere, grinding and sieving to obtain a vanadium-based glass powder; Mixing the vanadium-based glass powder and the impregnating solution, filtering, and carbonizing to obtain a carbon-coated active substance glass powder.

6. The preparation method according to claim 5, characterized in that The carbonization specifically includes: In an N2 atmosphere, heating to 1500~1800°C, holding for 10~300 min; then continuing to heat to 2000~3000°C, holding for 10~30 min, and cooling to obtain a carbon-coated active substance glass powder.

7. The preparation method according to claim 5, wherein Melting and quenching in an inert atmosphere specifically includes: Heating the mixture to 500~800°C in an inert atmosphere, holding for 10~300 min, then continuing to heat to 1000~2000°C, holding for 10~30 min, and cooling to obtain a glass block.

8. An amorphous cathode material, comprising the carbon-coated active substance glass powder according to claim 1, a binder, and a conductive filler; The mass ratio of the carbon-coated active substance glass powder, the binder, and the conductive filler is (6~10) : (2~3) : (1~2).

9. A lithium-ion battery, comprising the amorphous cathode material according to claim 8.

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